Most of the 3D-printed scale models you’ve seen have probably been relatively small. This project is anything but. You can actually walk inside this castle; it’s going to be more than 10 feet tall when it’s finished. The massive printer that’s laying down the concrete castle is the creation of Minnesota engineer Andrey Rudenko.

3D printing a building isn’t a new achievement — several Chinese firms have already been experimenting with concrete printing for some time. Back in April, Winsun New Materials successfully printed 10 homes in just 24 hours. With their system, a series of panels were created and then positioned by a human crew.

Rudenko’s setup appears to be just as flexible as a desktop printer like a MakerBot or Cubify. It lays down row after row of concrete directly onto the building site. Rudenko says the printer is capable of churning out between 75cm and a full meter in ideal curing conditions without risk of collapse.

For his castle project, he stuck to a more conservative 50cm. That’s how high the uncured dark gray portion you see is, and it took around eight hours to print. At a meter and a half per day, printing out the scaled-down castle could be completed in just a few days.

Now that he’s proven his printer is capable of printing a large structure out in the elements, Rudenko is polishing off plans for his next project: 3D-printing a two-story house. It’ll be ready for the cold Minnesota winters, too. The printer lays down concrete in a path two centimeters wide, leaving a nice, wide cavity that can be filled with whatever insulating material he chooses to keep Jack Frost at bay.

Thinking about whipping up your very own house-sized 3D printer? You probably could: Rudenko’s design is based on the open source RepRap. He’s been working for well over a year to finalize the design, however, and he’s had to do a lot of tweaking to the delivery system to make it work. Most concrete pumps are built to work with material that’s a bit soupier, and that wouldn’t play well with a 3D printer.

Rudenko did a lot of tweaking to his concrete mix to get just the right viscosity, and he’s still adjusting things for outside use. So far so good. We can’t wait to see what the finished castle looks like — and how his house turns out.